Since 1996, when the Pew Research Center began polling on the issue, opponents of legalizing same-sex marriage have consistently outnumbered supporters, although by varying margins at different points in time. For instance, in 2004, just months after Massachusetts became the first state to allow gay marriage, a joint survey by the Pew Research Center’s Forum on Religion & Public Life and the Pew Research Center for the People & the Press found that about twice as many Americans opposed legalizing same-sex marriage (60%) as supported it (29%). More recently, an April 2009 survey by the Pew Research Center for the People & the Press found that opposition to legalizing same-sex marriage stood at 54%, with 35% supporting the right of gays and lesbians to wed. (See A Contentious Debate: Same-Sex Marriage in the U.S.)

As with many other social issues, opinions about same-sex marriage are closely linked with political affiliation. For instance, opposition to gay marriage is lowest among self-described Democrats (41%) and highest among self-described Republicans (77%).

The opinions of those who identify themselves as political independents roughly mirror those of the national population, with 55% of political independents opposed to same-sex marriage and 34% in favor of it.

The April 2009 Pew Research Center survey also found that opponents of same-sex marriage outnumber supporters by the widest margin among older people, with those over age 65 opposing gay marriage by a margin of 64% to 24%. By contrast, those under age 30 are about evenly divided on the issue, with 43% in favor of legalizing gay marriage and 45% opposed.

Some of the largest differences on the question of gay marriage occur among religious groups. For instance, those who say they attend worship services at least once a week are much more likely to oppose same-sex marriage (69%) than those who say they attend less often (45%).

Opinion also varies considerably by religious tradition. While about eight-in-ten white evangelical Protestants (81%) oppose gay marriage, opposition among white mainline Protestants (55%) and African-American Protestants (56%) is more in line with the population as a whole (54%). Meanwhile, in spite of the Catholic Church’s outspoken opposition to same-sex marriage, Catholics are closely divided on the issue, with 45% opposing gay marriage and 39% favoring it. Among the religiously unaffiliated population, a much smaller number (25%) opposes same-sex marriage. (See Religious Groups’ Official Positions on Gay Marriage.)

Public Opinion on Same-Sex Civil Unions

While a majority of Americans oppose same-sex marriage, a slight majority supports allowing gay and lesbian couples to enter into legal agreements that give them many of the same rights as married couples, a status commonly known as civil unions. Americans favor civil unions by a 53% to 39% margin, according to the April 2009 Pew Research Center poll.

Public Opinion on Adoption by Same-Sex Couples

Finally, public opinion is divided on the issue of allowing gays and lesbians to adopt children. According to a joint August 2008 survey by the Pew Research Center’s Forum on Religion & Public Life and the Pew Research Center for the People & the Press, about the same number say they favor allowing adoptions by same-sex couples (46%) as say they oppose it (48%).

Among religious groups, majorities of white mainline Protestants (56%) and white non-Hispanic Catholics (54%) express support for allowing gays and lesbians to adopt children. In contrast, white evangelical Protestants and black Protestants oppose the practice by large margins, with 66% of white evangelical Protestants and 60% of black Protestants expressing opposition to adoption by same-sex couples.

This report was written by David Masci, Senior Research Fellow, Pew Research Center’s Forum on Religion & Public Life.

About Pew Research Center Pew Research Center is a nonpartisan fact tank that informs the public about the issues, attitudes and trends shaping America and the world. It conducts public opinion polling, demographic research, media content analysis and other empirical social science research. Pew Research Center does not take policy positions. It is a subsidiary of The Pew Charitable Trusts.